Why, Do You Know, Why Reasons

Do you know the 'why' reasons, or, do the 'whys' often bother you for scientific explanations? For instance, you do know that stars twinkle, but do you know the reasons why, and how? Or, do you know the 'why' reasons behind falling in love? Or, do you know the reasons why dogs bury bones? Probably many of you don’t! Why Corner – the 'why' blog, answers these 'whys' for basic knowledge, with real reasons for the 'why' facts. So, just know them all here if you have the 'why' urge, that is!

Nov 19, 2007

Do you know why mosquito bites itch?

Prof. Know Why answers:

Mosquitoes are the familiar flying insects belonging to the family of Culicidae. There are about 2,500 known species of mosquitoes in the whole world. Mosquitoes are particularly dangerous insects since they are known to transmit such serious diseases as yellow fever, malaria, filariasis dengue and Japanese B encephalitis.

Mosquitoes generally bite at any time, but prefer the evening. And, do you know that only the female mosquitoes bite? Yes! The male mosquitoes, and sometimes the female mosquitoes, feed on nectar and other plant juices. But in most species the female mosquitoes require a blood meal to acquire protein, needed to produce eggs. Female mosquitoes lay multiple batches of eggs during their lifespan, and a new blood meal is needed to produce every batch. Different mosquito species prefer different host species. Some mosquitoes seek blood meals from birds, while other mosquitoes love mammals. And some are generalists.

But why do mosquito bites itch? The female mosquito inserts her needle-like proboscis (a slender, tubular, feeding and sucking organ) into the victim's skin, to draw blood. She sucks until her abdomen is full. But doing that is not easy as blood clots very quickly (on contact with air) to have a drink. So, the mosquito injects her saliva, containing digestive enzymes and anticoagulants that stop the blood from clotting. Our body sees that as an enemy and produces and sends chemical called histamines to the injected area, to ward off infection. And, it’s the reaction between histamines and the saliva of the mosquito that causes the itching, swelling and redness.

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